Engine deposit removal



United States Patent ENGINE DEPOSIT REMOVAL Paul E. Oberdorfer, Jr.,Clayrnont, Del., assignor to Sun Oil Company, Philadelphia, Pa., acorporation of New Jersey No Drawing. Application November 15, 1956Serial No. 622,256

4 Claims. (Cl. 252143) This invention relates to a process for removingdeposits from the combustion chambers of internal combustion engines,and to compositions of matter suitable for use in such a process.

It is well known to the art that during the operation of an initiallyclean internal combustion engine, deposits form and accumulate onsurfaces within and adjacent to the combustion zone, such as on thecylinder head, spark plugs, piston tops, and valves. These deposits havea number of adverse effects on engine operation, for example, they causean increase in the octane requirement of the engine, and also contributeto preignition with con-,

sequent roughness of operation. The problem of engine deposits isparticularly acute when tetraethyl lead is contained in the fuel, sincethe deposits in this case contain an appreciable amount of leadcompounds which adhere firmly to the surfaces on which they aredeposited, and which contribute to shorting of the spark plugs, withconsequent loss of power.

It is an object of this invention to provide a series of solventformulations which are highly efiective, when brought into contact withengine deposits containing lead, to soften and loosen the deposits to adegree such that, on starting the engine after such contacting, thedeposits will break off the surfaces to which they are attached and willbe blown out the exhaust, leaving the surfaces in the combustion zoneessentially free of deposits.

In my application, United States Serial No. 595,055, filed July 2, 1956,of which the present application is a continuation-in-part, I disclosedthat cyclic carbonate inner esters having the formula:

RgC-O 9 RgC-O were effective in removing engine deposits. In thatapplication, I disclosed a preferred solvent formulation comprisingpropylene carbonate, ethyl acetate, and ethylene glycol monoethyl ether.This solvent is highly effective in removing gummy deposits fromrelatively cool surfaces, such as surfaces of a carburetor, and is alsoeffective to a degree in removing deposits from surfaces in thecombustion zone of an engine.

I have now found that if aqueous acetic acid is included as a componentof the solvent formulation, superior results may be obtained in removingdeposits from the combustion chambers of internal combustion engineswhich have been operated with a leaded gasoline. The reason why theacetic acid contributes to the effectiveness of the solvent formulationis not definitely known, but it may be that it converts the leadcompounds in the deposits to soluble lead acetates, which dissolveduring the power stroke of the piston, so that they no longer sticktenaciously to the surfaces to which they are attached, and may beeasily removed in conjunction with the carbon deposits loosened by thecarbonate inner ester component of the solvent.

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The preferred compositions of the present invention comprise from about10% to about 70% of a cyclic carbonate inner ester, from about 10% toabout 30% of a low-boiling polar solvent such as acetone, dimethylacetal, methylal, methanol, methyl ethyl ketone, ethanol, isopropanol,ethyl acetate, and the like, and from about 20% to about 60% aqueousacetic acid, which may range in strength from about 25% to about.Alternatively, a compound which yields acetic acid when exposed to theconditions obtained in the cylinders of an engine under operation, suchas aceto-acetic ester, benzal diacetate, acetone diacetate, etc., may beused in place of the acetic acid. The cyclic carbonate inner ester hasthe formula:

in which R may be hydrogen or a hydrocarbon radical. Typical of suchesters are ethylene carbonate:

HzC-O C=O H2C"0/ propylene carbonate:

butylene carbonates:

amylene carbonate:

H 05H1-C-0 C=O and its isomers HzC-O and higher homologues of the abovecompounds. While in the compounds specifically shown above thehydrocarbon substituents are alkyl, they may also be aryl, alkenyl, oralkaryl, for example, suitable compounds would include phenylethylenecarbonate, methyl phenylethylene carbonate, or vinylethylene carbonate.I prefer to use carbonates which have a boiling point sufficiently highthat they do not immediately vaporize upon introduction into thecylinders of an idling engine, since in order to make effective contactwith the engine deposits, it is necessary that the carbonate beintroduced into the cylinder as a mist which condenses on he surfaces tobe treated as a liquid film, in order to effect proper penetration ofthe deposits. I prefer to use propylene carbonate or higher molecularweight carbonates. If, however, the carbonate is of very high molecularweight, since its solvent power depends on the cyclic ester group, it isobvious that much larger quantities must be used in order to introduceinto the engine the same number of cyclic ester groups as when usinglower molecular weight esters. For this reason, I prefer that there benot more than about six to nine carbon atoms in the substituenthydrocarbon groups, although for special applications, such as whenlubricity in the cleaning composition isdesired, higher molecular weightesters may be used. The low-boling polar solvent component of my newcompositions is used chiefly to control their viscosity, but it isthought that it FORMULA 1 Percent Propylene carbonate Acetone 25 50%acetic acid 50 FORMULA H Butylene carbonates -1 40 Methyl ethyl ketone75% acetic acid 30 FORMULA III Amylene carbonate 50 Methanol 15 60%acetic acid FORMULA IV Propylene carbonate 25 Acetone 25 Acetoaceticester 25 Water 25 In order to illustrate the effectiveness of my newcompositions in cleaning deposits from the cylinders of internalcombustion engines, the following examples are given:

Example I A freshly cleaned 1956 Oldsmobile engine was tested at 2000rpm. and was found to have a power output of 102.1 HP. and an octanerequirement of 87. The engirls was run for 120 hours on a leadedgasoline. On retesting it was found that the power output had dropped to80.3, and the octane requirement had increased to 95. The spark plugswere then removed and replaced with new plugs, and the engine wasretested. It was found that the power output increased to 100.1, but theoctane requirement remained fairly constant at 93. This indicated thatspark plug fouling had been the cause of the loss of power, but otherdeposits in the cylinders were responsible for the increase in octanerequirement. The new plugs were then taken out and the old dirty onesreplaced without cleaning.

'The engine was then restarted, brought to full operating temperatureand throttled to a fast idling speed. The air cleaner was then removed,and about one and onequarter pints of Formulation I were dripped intothe carburetor air intake at the maximum rate which would just preventengine stalling. A final quarter pint was then added as a slug to stallthe engine. Following a soaking period of about one hour, the engine wasrestarted and was run for about 20 minutes to blow out looseneddeposits. It was then retested and found to have a power output of 97.8HP. and an octane requirement of 88, which was virtually the same asthat of the engine when freshly cleaned. The engine was then taken apartand visually inspected. The surfaces in the combustion zones were foundto be essentially free of deposits.

Example II The same procedure as in Example I was followed in cleaningout a number of late model cars which had accumulated engine deposits innormal driving use. Significant reduction in octane requirement wasobtained in all cases, as indicated in the following table.

Octane Number Requirement Car Before After Cleaning Cleaning 1956 FordFairlane 90 84. 5 1955 Buick Super 96.4 94 1956 Mercury 96. 4 93.5 1954Oldsmobile 88 93.2 90. 6 1954 Oldsmobile 98 93.8 89.6

I claim:

1. The method of removing deposits from an internal combustion enginewhich comprises contacting the deposits with a composition comprisingfrom about 10 to about volume percent of. a cyclic carbonate inner esterselected from the group consisting of ethylene carbonate, propylenecarbonate, butylene carbonate and amylene carbonate, from about 10 toabout30 volume percent of an organic polar solvent selected from thegroup consisting of acetone, dimethyl acetal, methylal, methanol, methylethyl ketone, ethanol and isopropanol, and mixtures thereof, and fromabout 20 to about 60 volume percent of an aqueous solution of a compoundselected from the group consisting of acetic acid and compounds capableof yielding acetic acid by thermal decomposition.

2. The method according to claim 1 in which the cor. position comprisesabout 25 volumes of'propylene carbonate, about 25 volumes of acetone,and about 50 volumes of fifty percent aqueous acetic acid solution.

3. A solvent formulation for the removal of engine deposits whichcomprises from about 10 to about 70 volume percent of a cyclic carbonateinner ester selected from the group consisting of ethylene carbonate,propylene carbonate, butylene carbonate and amylene carbonate, fromabout-10 to about 30 volume percent of an organic polar solvent selectedfrom the group consisting of acetone, dimethyl acetal, methylal,methanol, methyl ethyl ketone, ethanol, and isopropanol, and mixturesthereof, and from about 20 to about 60 volume percent of an aqueoussolution selected from the group consisting of acetic acid and compoundscapable of yielding acetic acid by thermal decomposition.

4. A solvent formulation for the removal of engine deposits whichcomprises about 25 volumes of propylene carbonate, about 25 volumes ofacetone, and about 50 volumes of 50% aqueous acetic acid solution.

References Cited in the file of this patent UNITED STATES. PATENTS OTHERREFERENCES Allpress et al.: J. Chem. Soc., vol. 125, pp. 2259-2264(1924).

Condensed Chemical Dictionary, 5th Ed., pp. 454 and 909 (1956), pub. byReinhold Pub. Corp., N.Y.

3. A SOLVENT FORMULATION FOR THE REMOVAL OF ENGINE DEPOSITS WHICH COMPRISES FROM ABOUT 10 TO ABOUT 70 VOLUME PERCENT OF A CYCLIC CARBONATE INNER ESTER SELECTED FROM THE GROUP CONSISTING OF ETHYLENE CARBONATE, PROPYLENE CARBONATE, BUTYLENE CARBONATE AND AMYLENE CARBONATE, FROM ABOUT 10 TO ABOUT 30 VOLUME PERCENT OF AN ORGANIC POLAR SOLVENT SELECTED FROM THE GROUP CONSISTING OF ACETONE, DIMETHYL ACETAL, METHYLAL, METHANOL, METHYL ETHYL KETONE, ETHANOL, AND ISOPROPANOL, AND MIXTURES THEREOF, AND FROM ABOUT 20 TO ABOUT 60 VOLUME PERCENT OF AN AQUEOUS SOLUTION SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID AND COMPOUNDS CAPABLE OF YIELDING ACETIC ACID BY THERMAL DECOMPOSITION. 